Nutrient Level, Trophic Status, Sediment-Water Interface And Determinant Factors In Dandi Lake, West Shoa Zone, Ethiopia

Abstract

Excessive nutrient load results in excessive. Hence, this study aimed to assess the external nutrient load, its sediment-water interface, trophic status, and determinant factors nutrient load in Lake Dandi. In this study, a longitudinal research design that includes both qualitative and quantitative primary data collection from water, sediment and respondents survey was used. Four sites were selected for the collection of water and sediment samples. The water temperature, pH, electrical conductivity (EC) and dissolved oxygen (DO) content in the water were measured in situ using a multiprobe meter, whereas the Secchi depth was measured using a 30cm Secchi disk. In addition, nutrient concentrations such as nitrite, nitrate, total phosphorus, total nitrogen, and ammonia in the water and sediments were measured in the laboratory. The highest mean temperature (19.42±0.710C), EC (155.18±6.48 µS cm-1)and DO (7.52±0.1 mgL-1)of water samples were recorded at the site 1, while the least amount was recorded at the site 2 accounting for 18.22±0.23 0C, 150.66±8.06 µS cm-1and 6.67±0.16 mgL-1, respectively. The highest and lowest pH was recorded at the site (8.65±0.36) and the Dandi Site 2 (8.24±0.80), respectively. On the other hand, the minimum (1.33 ±0.04 m) and maximum (1.78±0.15m) Secchi depth were recorded at the site 2 and the site 1, respectively. The highest water temperature (19.41±0.82 0C), pH (8.47±0.27), EC (159.08±1.57 µS cm-1) and SD (1.58±0.24m) were measured in the dry season (December to march) while the high DO content was obtained in the wet season (April to September) (7.21±0.3 mg-l). The mean TP, N-NO2, N-NO3, TN, and N-NH4+ contents recorded in the water samples collected this study were 7.57±1.90, 3.657±1.83, 12.6±2.95, 17.80±4.60 and 84.59±30.18 µg l-1, respectively with the highest contents recorded in D1 (4.54±3.40, 16.72±0.97, 9.66±0.704, 23.70±2.12 and 125.33±23.41µg l-1, respectively), whereas the least amount was recorded at the D3 site accounting for N-NO2, 2.78±0.18, and in D2 site for N-NO3, TP, TN and N-NH4+ 8.86±0.763, 5.22±0.61, 12.78±1.40 and 57.19±13.90µg l-1, respectively. The mean nutrient content in sediment samples for N-NO2, N-NO3, TP, TN and N-NH4+ were also 5.624±2.31, 16.07±4.74, 11.90 ±4.97, 23.87±7.77and 191.83±58.45 µg kg-1 with the highest and lowest result recorded at the D1 site and at the D2 site, respectively (p<0.05). Generally, the current study indicated that nutrient content is becoming an alarming issue with an expected eutrophication if appropriate measure not taken. This calls for an effective nutrient load management that engages all concerned bodies in the work.